The 50% Effective Dose Of Dexmedetomidine For Adequate Sedation Of Different Age Patients In Epiduralanesthesia

Objective To observe the 50% effective dose of dexmedetomidine for adequate sedation of patients undergoing lower limb orthopedic surgery in different age groups during epidural anesthesia.Methods Patients undergoing elective lower limb orthopedic surgery under epidural anesthesia,of American Society of Anesthesiologists physical status ⅠtoⅢ,were divided into three groups by age:Group young(25 to 44 years old),Group middle(45 to64 years old)and Group old(65 to 85 years old).Each group research done like the following: after the performance of epidural anesthesia with the block level adjusted below T10,a bolus dose of dexmedetomidine was administered via an injection pump for10 min.The initial dose of group old is 0.6 μ g/kg,in the other two groups is 1.0 μg/kg.The dose for each sequent was predetermined using a modified up-and-down method of Dixon(starting at an initial dose and step size of 0.05μg/kg).The sedative state would be assessed 30 minutes after the infusion of dexmedetomidine.The positive reaction for adequate sedation was defined by OAA/S is 3 and BIS <65 or OAA/S≤2.Record the dose of epidural anesthesia of each patients when the operation began.The degree of sensory block and motor block was assessed by pin-prick test and a modified Bromage Scale separately.Regression times of the motor and sensory block were recorded.Blood pressure(BP),heart rate(HR)and ECG were monitored during the operation of each patients.Record the incidence of adverse events of each group,such as hypotension,sinus bradycardia and others.Results The ED50 of Group Y was 1.03μg/kg(95% CI 0.92~1.74μg/kg),the ED95 was 1.21μg/kg(95% CI 1.10~2.93μg/kg).The ED50 of Group M was 0.76μg/kg(95% CI 0.72~0.80μg/kg).the ED95 was 0.84μg/kg(95% CI 0.80~1.15μg/kg).The ED50 of Group O was 0.40μg/kg(95% CI 0.32~0.45μg/kg).the ED95 was 0.54μg/kg(95% CI 0.46~1.62μg/kg).The dose of epidural anesthesia was less in Group O than in the two other groups(P<0.05).The sensory block was longer in Group O than inthe two other groups(P<0.05)and there was no significant difference in the time of motor block in the three groups.The incidence of hypotension was higher in Group O than in the two other groups.There was no significant difference in the incidence of sinus bradycardia in the three groups,but the incidence of atropine intervention was was higher in Group O than in the two other groups(P<0.05).Conclusion There were differences in dose-response relationship of dexmedetomidine for adequate sedation in patients of different age groups during epidural anesthesia.The old people were more sensitive to the sedation effect of dexmedetomidine.